The invention relates to the electrochemical processing of passages in components such nozzles, by passing an electrolyte through the passages. A switched-off operating current is measured after the end of each work cycle of the process, to determine a throughput of the electrolyte. This is a calibration procedure of the invention and takes place at a constant high pressure. Processing ends when the throughput quantity is equal to a selected throughput of the electrolyte measured at the same high pressure or of an equivalent test fluid used in a sample component. The high pressure of the electrolyte is maintained using another fluid which, together with the quantity of electrolyte is sufficient for the calibration procedure. The electrolyte and the other fluid are located in a common pressure storage chamber.
Such a method is disclosed in EP B 0 802 009. The object of the known method is to produce a pulsation-free electrolyte flow which is under a pressure on the order of 100 bar, during the calibration of the flow channels in the component, and whose throughput is measured and compared to a nominal value obtained from a sample component.
An important field of application is e.g. the calibration of injection nozzles which are used in motor vehicle engines. It is expected that very high operating pressures of diesel oil will be injected from these nozzles, at a very narrow tolerated throughput. In the known method it is assumed that nozzles which have the same electrolyte throughput during the calibration procedures, in a later application correspond also with respect to the diesel oil throughput, wherein this approach in any case leads to good results when the flowing through of electrolyte during calibration is roughly under the same pressure as the diesel oil during later operation of a motor vehicle using the nozzles.
In WO 90/05039 it is further assumed that the pressure difference in the very narrow nozzle channels, thus the flow speed prevailing in these channels, only plays a minor role and for example the viscosity difference between the electrolyte and the operating fluid later flowing through the nozzle body, e.g. diesel oil, is considered to be more important.
Modern diesel motors which use the so-called common-rail principle, function at operating pressures of more than 1000 bar and the demands of accuracy on the injection nozzles of course grow with the increase of the operating pressures. The previously mentioned method at these operating pressures reaches it limit because it is technically difficult, perhaps even impossible to obtain gas control valves of a sufficient accuracy for pressure regions of a magnitude of 1000 bar. Also the compressing of the gaseous foreign fluid to this high pressure value demands a high technical expense. Furthermore the costs for the large-volumed gas storer play a very negative role.
It is the object of the invention to improve the known method to the extent that the calibration of auxiliary components with their electrochemical processing under an electrolyte pressure of far above 100 bar may be carried out and specifically with a structure which, with an acceptable technical expense, keeps the electrolyte pressure reproducibly constant.
In contrast to the previously mentioned state of the art the electrolyte quantity required for the calibration is delivered practically without pressure into the electrolyte compartment of the pressure chamber, while an equally large fluid quantity is displaced from the fluid compartment of the pressure chamber into a pressureless reservoir. After the fluid compartment and the electrolyte compartment of the pressure chamber are blocked with respect to the reservoir and the electrolyte tank, which on the electrolyte side may be effected e.g. by way of a return valve, a high pressure pump provides the pressure build-up in the fluid compartment of the pressure chamber. The pressure constancy in the fluid compartment may be maintained very precisely with a fluid high pressure regulator, which in the case of a gas pressure regulatorxe2x80x94disregarding the incomparable high costsxe2x80x94would meet difficulties if one bears in mind the high pressures of the magnitude of 1000 bar. The electrolyte quantity exiting from the electrolyte compartment during the calibration must be continuously replaced with an equally large fluid quantity delivered by the fluid high pressure pump, which with a suitable design of the pump does not create any problems. The possible disadvantage with the method according to the invention, that pulsations are produced by the high pressure pump in the fluid compartment and are transmitted to the electrolyte, these then influencing the calibration procedure in a disturbing manner, in practice has surprisingly been shown to be unnoticeable, in particular when prior to the fluid compartment of the pressure storer there is connected a relatively large-volume damping buffer. It is essential that the pressure in the fluid compartment after completion of the calibration procedure is built up in that the outlet conduit to the reservoir is opened so that the new electrolyte quantity without pressure or at all events via a low counter-pressure can be delivered into the electrolyte compartment of the pressure chamber. The damping buffer however remainsxe2x80x94with the exception of the pressure build-up phase in the fluid compartmentxe2x80x94continuously under the high operating pressure and is also continuously connected to the high pressure pump, which demands a blocking of the high pressure pump delivery conduit together with the damping buffer from the fluid compartment of the pressure storer, when the fluid compartment is connected to the reservoir. This is possible by way of a simple reversing valve.
As a high pressure pump preferably a gear pump or a pump arrangement consisting of several gear pumps connected after one another is used. Alternatively it lies within the scope of the invention to use an axial piston pump as the high pressure pump. For the present invention it is important that, in the fluid compartment of the pressure chamber, there is achieved as slight a variation as possible over the time in the pressure.
A closed cylindrical container, roughly in the manner of a carbon dioxide cylinder, with a membrane incorporated to separate the fluid compartment from the electrolyte compartment has proven to be useful as a pressure chamber. Alternatively the pressure chamber can be a cylinder in which a piston is freely displaceable.